Telephone system



Feb- 12, 1935. H. M. FRIENDLY TELEPHONE SYSTEM Filed Dec. 19, 1951 4Sheets-Sheet 2 Feb. l2, 1935. M, FRlENDLY 1,990,644

TELEPHONE SYSTEM Fued Dec. 19, 1951 4 sheets-'sheet s In Ver/for-Friendly-Deceased Feb. 12, 1935. H. M. FRIENDLY 1,990,644

TELEPHONE SYSTEM Filed Dec. 19, 19:51 4 sheets-sheet 4 I n ven f o r H.M. Fr/ndly Jeu-eased Ml'lon 5. Friend/y and enf /epublfcan/f us[obra-afar.:

Patented Feb. 12, 1935 UNITED STATES PATE NT OFFICE TELEPHONE SYSTEMApplicationv December 19, 1931, Serial No. 582,110 27 Claims. (Cl.179-27) His present invention relates in general to telephone. systems,and more particularly to such systems as may be of the automatic orsemi-automatic type.

One of lthe objects of the present invention is to provide trunk lineswhich may be employedfor a dual purpose.

Another object is to provide means for enabling trunk lines extendingbetween various groups ci? automatic switches in one exchange or fromone -exchange to another to be used inthe usual manner and also topermit these trunk lines to be employed for special calls.

A further object is to consolidate special groups of trunk lines into asingle group to secure greater eiiciency. 1

` A still further object is to provide mechanism by which it is possibleto secure greater trunking efilciency by enabling a call to proceed froma calling to a called telephone subscriber over a route involving agreater number of stages ot selection than is called for by the calledsubscribers number.

Still anotherl object is to accomplish this result without undulyincreasing the complexity of the mechanism.

Still another object is to provide means for calling operators or otherspecial numbers over trunk lines that would be employed in the regularcourse of establishing a connection between two subscribers.

There are other objects of his invention which together with theforegoing will be described in the detailed speciiication that is tofollow, taken in conjunction with the accompanying drawings and forminga part thereof.

Referring now to the drawings, Fig. 1 is a schematic diagramillustrating the trunking arrangements for various connections in anautomatic telephone system employing his invention;

Figs. 2 and 3 illustrate by means of the usual conventional diagramssuiiicient of the apparatus in circuits employed to illustrate themanner in which trunk lines may be employed for`a dual purpose accordingto his invention;

Fig. 4 shows typical selector switches which may be employed in thesystem illustrated in Figs. 2 and 3 to extend a call to varioussubscribers.

Referring now more particularly to Fig. 1, the reference characters A,A1, A2, D, C, F, G, H, and I represent telephone instruments of variousautomatic telephone subscribers of any usual or well known type. Thereference Vcharacter M designates a manual telephone of any usual orwell known type. The lines of the telephones M,

A, A1. and A2 all terminate at their associated exchanges in lineswitches LS, LS1, LS2 and LS. These line switches may be of any usual orwell known type. The line ,switch of the manual telephone M has accessto trunk lines extending to a repeater R2 and thence to an incomingselector Q1*v at another exchange. The repeater Rn may be of any usualor well known type though in the present instance he has illustrated arepeater of the type in general use in Strowger step by step automatictelephone systems. The incoming selector Q3 is also of the Strowger typeslightly lmodiiied in accordance with his invention by the additon of anormal level of bank contacts and the provision that the switch mayrotate without first moving vertically. The trunk lines accessibleto-the incoming selector Q3 extend to other selectors P3 which are ofthe usual Strowger type commonly designated as Powell selectors. Thetrunk lines extending from the selectors P3 extend in the presentinstance to connectors D9 wherein access is obtained to subscriberstelephones such as F. The trunk lines terminating in the normal level ofincoming selectors Q3 may extend to operators positions such as thepositions of the toll recording operators indicated as O. The lines o fthe subscribers at automatic stations A terminating in line switchessuch as LS1 have access through these line switches to iirst selectorsof the usualv Strowger type such as P2, of which only four contacts ofeach level are shown by the four vertical rows oi ten contacts each tothe 'right of the wiper of P2. It is to be noted that the trunk lineextending through the repeater R2 to the incoming selector Q3 is alsoaccessible from the second level of bank contacts of certain of the rstselectors. The lines of the telephone stations such as A1 terminate inline switches L82 and have access through these line switches to rstselectors such as P16. The reference characters P1'7 and'P13 designateordinary selector switches while the reference character D19 designatesa group of connector switches. 'The lines of the subscribers such as A2terminate in line switches LS3 at a local or sub-exchange. The lineswitches LS3 have access to trunk lines extending through repeaters suchas R5 to incoming first selectors Q at the main exchange. The incomingfirst selectors Q are provided with a normal level for bringing aboutthe extension of a call by way of the normal level to an incoming secondselector such as P13 at another exchange. The trunk line extendingthrough tli'e repeater R5 may also be accessible as in the presentinstance froml the fifth level of the first selectors such as P2permitting the calls extending from this group of first selectors toextend through the sub-exchange and thence to the exchange at which thecall subscriber is located when the digit 5 is called. The variousincoming selectors designated. with the reference character Q indicatesincoming switches which are provided with a normal level. The referencecharacter P designates the usual type of Strowger selector switches.

In order to give the broad understanding of his invention he firstdescribes typical calls from automatic sub-station A to various callsubscribers. He iirst assumes that the subscriber at substation Adesires to call the subscriber at substation G whose number is 24641.The removal of thereceiver at sub-station A brings about the operationof the line switch LSI to extend the calling line to an idle firstselector P. The operation of the calling device at the station inaccordance with the digit 2 brings about the selection of a trunk lineextending through a repeater Rs to an incoming. second selector Q1 inthe exchange in which the subscriber at substation G is located. Theoperation of the calling device in accordance with the next digit 4brings about an extension of the calling line to an idle third selectorP10, the next operation of the calling device for the digit 6 bringsabout the operation'of the selector P10 and the extension of the callingline toan idle connector D11. The remaining two digits 41 serve toselect the called line. When the calling subscriber at sub-station Adesires to call -the subscriber at sub-station H whose number is 53321,the following operations occur: The selector P2 is operated to the 111thlevel in accordance with the rst digit and a direct trunk line in thefifth level leading toward the wanted exchange of station H is selectedextending to the incoming second selector P12 and thence by way of thisswitch through the selectors P14 and connector D15. In the event thatthe direct trunks are busy, a certain other or indirect trunk at the endcontact of the ilith level is selected extending from first selector Psuch as the one extending to the repeater R'1 this operation of dialingthe digit 5 for a call to the subscriber at sub-station H brings aboutthe selection of the trunk line extending through the repeaters R" atthe exchange of the calling line and the repeater R5 at the sub-exchangeto an incoming selector Q. The seizure of this trunk line brings aboutthe automatic operation of the selector Q on its normal level to selecta trunl-r line terminating in the incoming second selector P11. Theremaining dialing operations bring about the establishment of theconnection with the subscriber at substation H in the usual mannerthrough selectors P13 and P1* and connector D15. It will be seen thatthis call extends by way of the trunk line through the sub-exchange ofthe subscriber at sub-station A2 and that the selector Q is operatedautomatically to trunk this kind of a call through the main exchangeovera different path than that obtained in a previously establishedconnection from A to H. This alternative trunking route may beadvantageously employed to inincrease the etlicieney of the trunkingsystem.

When the subscriber at a manual telephone M desires to make a call,which call must be made by an operator, and removes his receiver, theoperation of the line switch LS extends the calling line through therepeater R2 to an incoming selector Q1. This operation causes theSelector Q11 to rotate on its normal level to extend the calling line toan operator O who may answer the call and establish Ache'connection asdesired. If thisoperator is employ'ed as a toll recording operator or acomplaint operator, it may be desirable to provide means by which theautomatic subscribers such as the one at sub-station A have access totrunk lines extending to this position. This is accomplished bydesignating the tenth or O level of the rst selectors for this use. theselector Pz is operated into the tenth level the subscribers line isextended through the incoming selector Q3 to the operator's position O.Other operators positions such as the one at E may be selected in asimilar manner by extending the trunk line C to the proper level ofselectors which may be employed for the handling of these calls, and analternative arrangement is illustrated for the trunk line C by means ofthe switch K whereby the operator's position E is rendered accessiblefrom the eighth level of the third selectors such as P5 or the fifthlevel of second selectors such as P1. This operator's position wouldthen be accessible upon dialing 45 or 438, depending upon the positionof the switch K. The selector Q4 is also accessible from the secondlevel of certain'groups of first selectors P2 and in this instance whena call is extended through the first selectors the incoming selector Q4would operate in the usual manner. Thus it will be seen that thearrangement described permits trunk lines to be employed for a dualpurpose in a larger group than heretofore. The usual practice inexigencies oi' this character where similar conditions are to be metinvolves the use of a separate group of trunks extending to eachoperator's position. By his invention, the trunk lines may beconsolidated into one group securing greater traflic emcency andconsiderably reducing the expense. Furthermore, the invention may beemployed to trunk through another exchange in a roundabout manner whichordinarily could not be accomplished in the ordinary use of a telephonesystem without the use of a device such as a director or translator. Hisinvention also permits manual telephones to be employed and terminate atan automatic exchange and have calls from these telephones handled by anoperator.

Having briey described the general process of setting up various callsin an automatic telephone system of his invention, he now explains thedetailed circuit arrangements and operations by which this isaccomplished.

v Referring now to Fig. 2, the reference character M in the upperlefthand corner thereof designates a manual telephone of the usual orwell known type. The line from the manual telephone terminates in a lineswitch LS. 'I'his line switch is of the usual or well known rotary typeand is provided with a line relay 101, switch- 'ing relay 100, motormagnet 102 and wipers 109 to lll inclusive. Motor magnet 102 serves tostep the switch wipers into engagement with bank contacts which areconnected to trunk lines extending to repeaters such as R2. The lines ofthe automatic subscribers such as at sub-station A terminate in lineswitches LS1 of a type similar to the line switches LS. The telephonestation A is of the usual automatic type. The line switches such as LS1have access to trunk lines extending to first selectors such as P2. Thefirst selectors such as P2 are of the usual and well known Powell typebeing provided with a ver tical magnet 120, rotary magnet 121, releaseWhen magnet 122 and control relays 115 to 119 inclusive. The selector P2is also provided with wipers 137 to 139 inclusive which have access tobank contacts on ten levels. The trunk lines terminating in the bankcontacts accessible to rst selectors extend to other selectors as may beseen in Fig. 1, and also to trunk lines extending through repeaters suchas R2 to incoming second selectors such as Q3 (Eig. 3) located at adiiferent exchange. The repeaters such as R2 are generally of the sametype as those ordinarily employed in automatic exchanges have thecontrolling relays 150 to 154 inclusive and 158. In addition therepeater R2 is provided with relays 155 and 156 which have a specialfunction in accordance with his invention as will appear.

The incoming second selector Q3 is of the usual and well known type ofStrowger switch with the exception that it is provided with a normallevel of bank contacts accessible to switch wipers 225 to 227 inclusive.The selector Q3 is also provided with a vertical magnet 206, rotarymagnet 207 and a release magnet 208, in addition to the controllingrelays 200 to 205 inclusive. The bank contact accessible to the switchwipers 225 to 227 inclusive on the normal level extend to operatorsposition such as O. On the other levels they may extend to thirdselector switches such as the selector P3. Selector P3 is of the usualstep by step type in common use. The circuits at the operators positionO may be of any usual or well known type. In certain instances there maybe a. large number of operators having different functions and it may bedesirable to select between them. I'his can be accomplished by theprovision of a selector such as P23 accessible from the normal level ofbank contacts of the incoming selector such as Q3. The selectors P23 aswell as the selectors P22 are similar to the selectors P3 previouslydescribed.

Having briefly described the circuits and apparatus necessary toillustrate his invention, he now explains their detailed operation. Forthis purpose, he assumed that the subscriber at the manual telephone Mdesires to make a telephone call. In order to accomplish this result,his line must be extended to an operator at the operators position O.This result is brought about in the following manner. When the receiveris removed at the manual telephone end, the two line conductors of thecalling end are bridged and there is a circuitJ completed which extendsfrom ground by way of back contact and armature 104talking conductors ofthe calling line armature 103 and its back contact and relay 101 tobattery. The relay 101 is energized over this circuit and operates toestablish a circuit for the switching relay at armature 108 in serieswith the motor magnet 102 and an armature 107 connects the'test wiper109 to the above circuit at a point midway between the switching relayand the motor magnet. If the trunk line with which the switch wipers 109to 111 inclusive is busy4 there will be a ground connected to the bankcontact engaged by the switch wiper 109. The switching relay 100 will beshort circuited and the motorrnagnet 102 will be operated intermittentlyto advance the switch wipers 109 to 111 inclusive into engagement withan idle trunk as designated by an absence of ground on the test contact.It will be assumed that this trunk line is the one terminating in thebank contacts 190 to 192 inclusive. When this occurs there will be acircuit effective for energizing the switching relay 100 in series withthe motor magnet 102.

The switching relay upon operating, opens a point in the test circuit atarmature 105momentarily connects ground to the test contact 109 at thefront contact of this armature, at the same time preparing a holdingcircuit for itself, and at armatures 103 and 104 disconnects the circuitof the line relay from the calling line and extends the talking circuitof the calling line by way of the front contacts of these armatures,wipers 110 and 111, bank contacts 191 and 192, relay 155, normallyclosed springs controlled by armatures and 161 of the repeater R2 to theupper and lower windings of the line relay 151. The line relay 151 isimmediately energized over the above circuit and operates to establish acircuit for the slow acting relay 152 at armature 163 and to place abridge across the trurik conductors and 181 at armature 164. It will benoted that the slow acting relay 155 is energized in series with theline relay 151. The relay 155 upon operating serves to complete acircuit for the supervisory lamp 157 at armature 174 to complete acircuit for the slow to operate relay 156 at armature 175 and to connectground tothe trunk conductor 180 at armature 176. This latter operationcompletes a circuit which extends from ground by way of armature 176 andits front contact trunk conductor 180, armature 211 and its back contactupper winding of line relay 201, and upper winding of differential relay202 to battery. Relays 201 and 202 are energized over this circuit. Theoperation of the armatures 214 and 215 of the relays 201 and 202 of theincoming selector Q3 serve to complete a circuit which extends fromground by way of armature 214 and its front contact armature 215 and itsfront contact, resting contact of ofi normal spring 217 and said spring,and relay 205 to battery. The relay 205 is energized over this circuit.Another result of the operation of the armature 214 is that there is acircuit completed for the slow acting relay 203. Slow acting relay 203opens a pointv in the release circuit at armature 219, prepares acircuit for the vertical magnet 206 at the front contact of thisarmature, and at armature 218 prepares circuits for the rotary magnet207 and the switching relay 200. The relay 205 is energized to completea circuit for the rotary magnet at armature 223. The rotary magnet 207is energized to advance the switch wipers 225 to 227 inclusive intoengagement with the rst set of bank contacts. At the rst rotary off.normal step of the switch the rotary off normal springs RS are closed,thereby preparing a test circuit for the test wiper 225. If the rsttrunk line engaged by the switch wipers 225 to 227 inclusive is busythere will be a ground potential present upon the bank contact engagedby the wiper 225 and there will be a circuit completed extending by wayof armature 210 and its back contact, back contact and armature 221,rotary off normal springs RS and relay 205 to battery. The relay 205will be energized over this circuit to establish a locking circuit foritself at armature 222 and to complete the rotary magnet circuit atarmature 223. The rotaryv magnet 207V will operate to advance the switchwipers another step into engagement with the next set of bank contactsand to open the locking circuit of the interrupter relay 205 at armature221. The alternate operations of the interrupter relay 205 and rotarymagnet 207 will continue until the switch wipers 225 to 227 inclusiveare brought into engagement with the set of bank contacts associatedwith an idle trunk line.

In the repeater R the relay 156 is energized after a short interval oftime to attract its arma,- tures, thereby establishing a locking circuitfor itself at armature 177 and at amature 178 short circuiting the relay155. The relay 155 is deenergized after a short interval of time toretract its armature 176, thereby opening the previously traced circuitfor relays 201 and 202 in the incoming selector Q2. 'I'hese relays arenot deenergized, however, for the reason that a new circuit has beenestablished for them by the placing of a bridge across the trunkconductors 180 and 181 by the operation of the relays 151 and 152 in therepeater R2. It should be noted at this time that when the relay 152 wasenergized as previously described, a holding circuit was established forthe switching relay in line switch LS. This bridging circuit for theenergizing of the relays 201 and 202 in the selector Q3 may be tracedfrom ground through the lower winding of the diierential relay 202,lower winding of line relay 201, back contact and armature 212, trunkconductor 181, front contact and armature 164, righthand winding of animpedance relay 158, normally closed springs controlled by armature 162,winding of electropolarized relay 154, normally closed springscontrolled by armature 169, front contact and armature 166, trunkconductor 180, armature 211 and its back contact, upper winding of linerelay 201, and upper winding of differential relay 202 to battery. Uponthe establishment of this circuit and after the deenergization of therelay in the repeater R2 the differential relay 202 retracts itsarmature while the armature 214 of the line relay 201 is maintainedattracted, This result follows for the reason that the current flowthrough both windings of the diierential relay 202 now oppose eachother. 'I'he retraction of the armature 215 opens the original circuitfor the interrupter relay 205 to permit the trunk selecting operation ofthe selector Q2 on the normal level already described. When an idletrunk line is encountered by the switch Wipers 225 to 227 inclusive,which it will be assumed is the trunk line terminating in the bankcontacts 235 to 237 inclusive there will be no ground potential presentupon the bank contact 235 and no circuit will be completed for theinterrupter relay 205. A circuit is thereupon effective which extendsfrom ground by way of front contact and amature 218, switching relay200, back contact and armature 221, rotary oi normal springs RS, andrelay 205 to battery. The switching relay 200 is energized over thiscircuit in series with the interrupter relay 205. The latter is notoperated to aiect its armatures by reason of the high resistance of theswitching relay. The relay 200 upon operating opens a point in thecircuit of the release magnet 208 at armature 213, opens a point in thetest circuit at armature 210, and its back contact, and at the frontcontact of this amature prepares a holding circuit for the relay 200,and at armatures 211 and 212 disconnects the trunk conductors and 181from the windings of the line relay 201 and extends them by way of theswitch wipers 226 and 227, bank contacts 236 and 237, trunk conductors305 and 306 to the windings of the battery supply relay 240. The batterysupply relay 240 at operators position O is energized over a circuitincluding the trunk conductors and operates to 4complete a circuit atarmature 242 for the slow acting relay 241. The slow acting relay 241upon energizing establishes a holding circuit for the switching relay200 of the selector Q2 at armature 243 and at amature 244, completes acircuit for the supervisory lamp L2.

In the selector Q2 the operation oi.' the relay 200 brings about thedeenergization of the line relay 201 and the consequent opening of thecircuit of the slow acting relay 203. The slow acting relay 203 isenergized to open a point in the circuit of the switching relay 200after a short interval of time. The switching relay 200 is nowmaintained energized by ground supplied by ths armature 243 of the relay241.

The lighting of the supervisory signal L2 apprises the operator that acall is waiting and she will throw the key K1 associated with the tnmkline seized and communicate with the calling party to ascertain hiswishes. She may then establish the remaining connection in any usual orwell known manner.

When the subscriber at sub-station M replaces his receiver upon theswitch hook, the relay 240 in the operator's trunk circuit isdeenergized to open the circuit of the slow acting relay 241. After ashort interval of timethe relay 241 is deenergized to open the circuitoi the switching relay 200. The switching relay 200 in the selector Q3is deenergized to complete a circuit for the release magnet 208 at therotary oi! normal springs RS. 'Ihe release magnet 208 operates torestore the switch wipers 225 to 227 inclusive to normal, whereupon itscircuit is opened at the oil normal springs RS. The equipment at thedistant exchange is thus restored to normal. This release operation ofthe equipment at the distant exchange occurs as a result of thedeenergization of the line relay 151 in the repeater R2 by the openingof the bridge across the trunk conductors 180 and 181 at armature 164.The deenergization of the line relay 151 also opens the circuit of theslow acting relay 152. The slow acting relay 152 is deenergized toremove ground from the release trunk conductor 179, thereby opening theholding circuit of the switching relay 100 in the line switch LS inaddition to opening the locking circuit of the slow to energize relay156. The slow to energize relay 156 is deenergized to remove the shortcircuit from the relay 155 at armature 158 and to open its lockingcircuit at armature 177. The deenergization of the switching relay 100in the line switch LS restores the circuits of the line switch tonormal.

The equipment employed in the call is released in the above manner.

It is now considered that the subscriber at substation A who has anautomatic telephone desires to make a call to another subscriber whosenumber is such that his line is accessible over the trunk linesextending from repeaters such as R2. In order to accomplish this resultthe subscriber at sub-station A will remove his receiver from the switchhook and dial the digits of the call subscribers number, the first digitbeing 2 in the present instance.

Responsive to the removal of the receiver at the calling telephone A,the line switch LSl which may be of the same type as the line switch LSis operated in a manner similar to that already described to select atrunk line extending to an idle rst selector which it will be assumed isthe tlrst selector P2. As a result of the extension of the calling lineby the line switch LS1, line relay 116 of the iirst selector P2 isenergized to establish a circuit for the slow acting relay 117. The slowacting relay 117 is operated to prepare a circuit for the verticalmagnet at armature 129, and to establish a holding circuit for the lineswitch LS1 at armature 128. 'I'hese operations occur responsive to theremoval of the receiver at the calling station A.

When the calling device at sub-station A is operated in accordance withthe first digit 2 of the call subscribers number two interruptions willbe produced in the circuit of the line relay 116 and this relay willretract its armature 127 twice. At each retraction oi' the armature 127there is a circuit completed which extends from ground by way of saidarmature and its back contact, back contact and amature 126, armature129 and its front contact, slow acting relay 118 and vertical magnet 120to battery. operated to raise the switch wipers 137 to 139 inclusive twosteps opposite the second level of bank contacts. The slow acting relay118 is en` ergized in series with the vertical magnet 120 and operatesto complete a circuit which extends from ground by way of front contactand armature 128, amature 132 and its front contact off normal spring131 and its working contact and interrupter relay 119 to battery. Theinterrupter relay is energized at the irst o ff normal step of theswitch to prepare a circuit for the rotary magnet 121 at'armature 135and to establish a locking circuit for itself at armature 134. A shortinterval after the cessation of the operation of the line relay 116 theslow acting relay v118 is deenergized to complete a circuit for therotary magnet at armature 132 and its back contact. The rotary magnet121 is energized to advance the switch wipers 137 to 139 inclusive intoengagement with the first set of bank contacts on the second level. Therotary magnet also brings about the opening of the locking circuit ofthe relay 119 at armature 133. Relay 119 is deenergized to open thecircuit of the rotary magnet 121 which is also deenergized. If the bankcontacts engaged by the switch wipers 137 to 139 inclusive areassociated with a busy trunk line, there will be a ground potentialpresent upon the test contact engaged by the switch wiper 137 and therewill be a circuit completed extending from said ground armature 123 andits back contact, back contact and armature 133, off normal spring 131and its working contact and interrupter relay 119 to battery. Theinterrupter relay 119 will be energized over this circuit to establish alocking circuit for itself at armature 134 and to complete a circuit atarmature 135 for the rotary magnet 121. The rotary magnet 121 isenergized to advance the switch wipers into engagement with the next setof bank contacts and to open the circuit of the interrupter relay 119.The interrupter relay 119 and the rotary magnet 121 continue to operatealternately until the switch wipers 137 to 139 inclusive are broughtinto en.- gagement with the bank contacts associated with an idle trunkline which it will be assumed arethe bank contacts 141 to 143 inclusive.In this instance there will be no ground potential present upon the bankcontact 141 and no circuit will be completed for the interrupter relay119. A circuit is now effective for the switching relay 115 whichextends from ground by way of front contact and armature 128, relay'115,back contact and armature 133, oif normal spring 131 and its workingcontact, and relay 119 to battery. The switching relay 115 is the 'onlyone operatively .energized over the abovecircuit because of its highresistance. The relay 115 upon operating opens a` point in the circuitof a release magnet The vertical magnet is gized over a circuitincluding the calling line and operates to complete a circuit for theslow acting relay 152 at armature 163 and to complete a bridge acrossthe trunk conductors and 181 at armature 164 and the slow acting relay152 is energized to prepare a circuit for the slow acting relay 153 atarmature 168 to complete another point in the bridge circuit across thetrunk conductors 180 and 181 at armature 166, and to complete thecircuit for the polarizing winding of the electropolarized relay 154 atarmature 167. A furtherresult of the operation of the relay 152 is thatat armature 167 there is a holding circuit established for the switchingrelay 115 of the selector P2 and the holding relay of the line switchLS1. This holding circuit is established prior to the deenergization ofthe slow acting relay 117 of the selector P2 which occurs a shortinterval of time after the deenergization of the line relay 116following the operation of the switching relay 115.

The bridge across the trunk conductors 180 and 181 establishes a circuitfor the line relay 201 of the incoming selector Q3 over a path that maybe traced from ground, lower winding of differential relay 202, lowerwinding of line relay 201, back contact and armature 212, conductor 181,front contact and armature 164, right-hand winding of impedance relay158, normally closed springs controlled by armature 162, winding ofpolarized relay 154, normally close'd springs controlled by armature169, front contact and armature 166, trunk conductor 180, armature 211and its back contact, upper winding of line relay 201 and upper windingof differential relay 202 to battery. The diierential relay 202 is notoperated over the above circuit since the current flow in its upper andlower windings oppose. However, the line relay 201 is energized tocomplete a circuit for slow acting relay 203. The slow acting relay 203is energized to open a point in the circuit of the releasing magnet atarmature 219 'slow acting relay 153 is energized to change the bridgeacross the trunk conductors 180 and 181, excluding the windings of therelays 158 and 154, the bridge extending from conductor 181 frontcontact and armature 164, armature 169 and its front contact, frontcontact and armature 166 to trunk-conductor 180. At each retraction ofthe armature 164 this bridge circuit which includes the line relay 201of the incoming selector Q3 is interrupted. The relay 201 is thusdeenergized twice to retract its armature 214. At each retraction of thearmature 214 of the selector Q3 there is a circuit completed whichextends from ground by way of armature 214 and its back contact, backcontact and armature 213, armature 219 and its front contact, relay 204and vertical magnet 206 to battery. The vertical magnet 206 is operatedto raise the switch wipers 225 to 227 inclusive opposite the secondlevel of bank contactsk exclusive of the normal level. The slow actingrelay 204 is energized in series with the vertical magnet 206 and uponthe nrst oif normal step of the switch completes the circuit whichextends from ground by way of front contact and armature 218, armature220 and its iront contact, working contact of of! normal spring 217 andsaid spring, and interrupter relay 205 to battery. The interrupter relay205 is energized to establish a locking circuit for itself at armature222 and to prepare a circuit for rotary magnet 207 at armature 223. Ashort interval of time after the cessation of impulses to the verticalmagnet the slow acting relay 204 is deenergized to complete a circuitfor the rotary magnet at armature 220 and its back contact. The rotarymagnet 207 is energized to advance the switch wipers 225 to 227inclusive into engagement with the first set of bank contacts on thesecond level. 'I'he operation of the rotary magnet also brings about theopening of the locking circuit of the interrupter relay 205 at armature221 and this relay is deenergized to open the circuit of the rotarymagnet which is also deenergized. l

In the repeater R2 a short interval of time after the restoration of thecalling device at calling sub-station A to normal, the slow acting relay153 is deenergized to restore the bridge across the trunk conductors 180and 181 in the repeater R3 to include the windings of the relays 154 and158.

In the selector Q3 if the rst set of bank contacts on the second levelare associated with a busy trunk line there will be a ground potentialpresent upon the bank contact engaged by the test wiper 225 and acircuit will be completed for interrupter relay 205. The interrupterrelay is energized to establish a locking circuit for itself and tocomplete a circuit for the rotary magnet 207. The alternate operation ofthe interrupter relay 205 and rotary magnet 207 continues until theswitch wipers 225 to 227 inclusive are brought into engagement with thebank contacts associated with an idle trunk line which it will beassumed are the bank contacts 230 to 232 inclusive.

In this instance there will be no ground potential upon the test contact230 and the rotary operation of the selector Q3 will cease. The circuitls thereupon effective for the switching relay 200 in series with theinterrupter relay 205. The operation of the switching relay 200 extendsthe calling) line by way of the wipers 226 and 227 trunk conductors 301and 302, armatures 261 and 262 to the upper and lower windings of theline relay 248 of a third selector P3. The line relay 248 is operatedover a circuit including the bridge across the trunk conductors 180 and181 at repeater R3. The line relay 248 upon operating completes acircuit for the slow acting relay 247 at armature 259. The slow actingrelay 247 is energized to prepare the circuit of the vertical magnet 252at armature 258,.and to place ground upon the release trunk at armature257, thereby establishing a holding circuit for the switching relay 200of the selector Q3. lished prior to the deenergization of the slowacting relay 203 which follows a short interval of time after thedeenergization of the line relay 201 This holding circuit is establcircuit ofthe line relay 151 of the repeater R2.

By the operation of the line relay 151 a corresponding number ofinterruptions will be produced in the circuit of the line relay 248 ofthe third selector P3. The deenergizations of the line relay v248 bringAabout the operation of the vertical magnet 252 to raise the switchwipers 270 to 272 inclusive opposite the proper level of bank contacts.Relay 246 is energized in series with the vertical magnet and operatesto complete a circuit for the interrupter relay 245. The interrupterrelay is energized to establish a locking circuit for itself and toprepare a circuit for the rotary magnet 251. A short interval of timeafter the cessation of interruptions in the circuit of the line relay248 the slow acting relay 246 is deenergized to complete the circuitofthe rotary magnet. The rotary magnet is operated to advance the switchwipers into engagement with the bank contacts associated with the rsttrunk line on the level selected. The trunk selecting operations occurin the same manner as before described in connection with the selectorQ3. When an idle trunk line is selected the switching relay 249 isenergized to extend the calling line to the connector switch.

The connector is operated in accordance with the last two digits in thecalled number to select the call line in any usual or well known manner.When the called party answers, the direction of current flow over thetrunk circuit including the electropolarized relay 154 is reversed tobring about the energization of this relay in the repeater. 'I'heoperation of the relay 154 brings about the completion of the talkingcircuit at armature 172 and the energization of the relay 150 atarmature 173. The relay 150 is operated to reverse the connections ofthe line relay 151 with respect to the calling line for metering orother purposes.

When the conversation is terminated the replacement of the receiver atVthe calling substation A brings about the deenergization of the linerelay 151. As a result of this operation the bridge across the trunkconductors 180 and 181 is opened at armature 164 and the relay 152 isdeenergized after a shorter interval of time. The deenergization ofrelay 152 removes ground from the release trunk conductor therebyopening the holding circuit of the switching relay 115 cf the ilrstselector P2 as well as the circuit of the switching relay of the lineswitch LS1. The selector P2 and line switch LSl are restored to normalresponsive to this operation. The release of the switches Q3 and P3follows as a result of the deenergization of the line relay in theconnector switch in any usual and well known manner. From the foregoingit will be seen that the trunk line comprising conductors 180 and 181 iscapable of special uses, this trunk line being one of a number which maybe employed for calling various operators in a manner similar to thatalready described. It will be seen that the trunk line is really dividedinto two portions at the incoming end. When seized over one of thebranches the selector Q3 is caused to operate to select an idle trunk onits normal level and extend the ,calling line to an operators position.When seized over the other branch the incoming selector functions in theusual manner. i

It maybe desirable to have the operator at position O function as a tollrecording operator and in this instance it is desirable that theautomatic subscribershave access to trunk lines extending to thisposition. 'I'his is illustrated in Fig. 2 by assigning the tenth or oldlevel of the first selectors for such calls. It will be seen that whenthe calling subscriber at substation A desires to call the operator at Othat the operation of the calling device at station A for this digitwill bring about the operation of the selector- P2 to select an idletrunkon the tenth level. It y will be assumed that this trunk lineterminates in the bank contacts 144 to 146.inclusive, and that this isselected by the selector P2.` As a result ofthis operation the relays155 and 156 function to bring about the energization of the\differential relay 202 in the incoming selector Q2. As a result of thisvoperation the selector Q3 is caused to rotate on its normal level andselect an idle trunk line leading to the operators position at O.

As mentioned before, it may be desirable to have a number of operatorspositions accessible over the trunk lines leading to selectors such asQ3.

This result can be accomplished by providing a selector such as P2sinterposed between the operators positions and the normal level of theselectors such as Q2. This arrangement is shown in Fig. 4. In thisinstance in order to select an operators position another digit must bedialed by the calling subscriber to operate the -selector such as P23 toselect the desired group of operators. The selector P22 in lthisinstance is an'ordinary third selector. Selectors such as P23 are alsoordinary selectors and function in anobvious manner.

From the foregoing the. functioning of his invention including thedivided trunk and other special instances as brieflydescribed inconnection with the trunking diagram of Fig. 1 will be obvious. Inspecial instances it will be seen that a trunk line of this charactermay be employed to trunk tandem througha plurality of exchanges wheresuch a result is necessary for the ideal or economical distribution oftrailic.

It is to be pointed out that the incoming selectors such as Q3 arebrought into operation lat the same time that the repeater R2 is seizedlso that no time is lost in the extension of the call to the operatorsposition.

It will be seen that his invention obviates the use of special trunksfor certain purposes such asA the calling of operators. The plan may beused in effecting calls to very special operators or telephones enablinga large general traflic trunk group to handle special traiiic. Generaltraiic may be handled by any and all trunks while trafiic to variousoperators may be-routed over certain of these general traflic trunkswhich are asline having two branches, an automatic-switch,

telephone lines, means for directively controlling said switchover onebranch of said trunk line to establish a connection with one of saidlines. and

means automatically operative when said `trunk line is seized over theother branch for establishing a connection with another of said lines.

2. In an automatic telephone system, a trunk line having two branches,an automatic switch, telephone lines and operators position, means fordirectively controlling said switch over one branch of said trunk lineto extend a connection in the direction of one of said telephone lines,and means automatically operative as 'a result of seizing the trunk lineover the other branch for extending said connection to said operatorsposition.

3. In an antomatic telephone system, a trunk line extending from a firstexchangeV to a second exchange and terminating at the second exchange inan incoming selector, a pair of branches for said trunk line at saidfirst exchange, means op- \erative over said trunk line when seizedthrough one of said branches for directively-controlling said selector,and means operative over said trunk line when seized over the other ofsaid branches vfor automatically operating said selector.

4. In a telephone system, a trunk line extending from the lrst exchange-to the Vsecond exchange, a repeater associated with said trunk line inthe iirst exchange, a selector switch associated with said trunk line insaid second exchange, said trunk line having a plurality of branches atthe rst exchange, means operative over said trunk line when seized overone of said branches for l:directively controlling said selector, andmeans operative as a result of seizing said trunk line over another ofsaid branches for automatically operating said selector.

5. In a telephone system, a trunk line extending from the first exchangeto the second exchange, a repeater associated with said trunk line inthe rst exchange, a selector switch associated with said trunk line insaid second-exchange, said trunk line having a plurality of branches atthe rst exchangameans operative over said trunk line when seized overone of said branches for directively controlling said selector, andmeans associated with said repeater automatically operative whensaidtrunk line is seized over another of said branches for bringing aboutthe automatic operation of said selector. y

6. In a telephone system, a trunk line terminating in an automaticswitch, vsaid trunk line having a' plurality of branches, meansoperative when said trunk line is seized over one of said branches fordirectively controlling said switch, and means operative when .the trunkline is seized over another of said branches for initiating an automaticoperation of said switch. 4

7. In a telephone system, a trunk. line terminating in an automaticswitch, said trunk line having two branches, means associated with oneof said branches for operating said switch, means operative over theother of said branches for directively controlling said switch, andmeans voperative as a result of seizing said trunk line over the firstmentioned branch for initiating the operation of Vsaid operating means.

8. In a telephone system, telephone lines directively controlledautomatic switches for establishing talking connectionsbetween saidlines, `each connection employing a predetermined Vnumber of directivelycontrolled switches and 9. In a telephone system, telephone lines, autonmatic switches directively controlled from any calling one oi' saidlines for establishing a conncction with a called one of said linesthrough a predetermined number of said switches serially related, andmeans for establishing a talking connection between said calling andcalled lines through a greater number of said switches serially relatedand directively controlled from said calling line.

10. In a telephone system, a trunk line terminating in an automaticswitch, said trunk line having three branches, means operative when saidtrunk line is seized over one of said branches for directivelycontrolling said switch, and means operative as a result of seizing saidtrunk line over either of the other branches for automatically operatingsaid switch.

11. In a telephone system, manual and automatic lines, a trunk line andoperators position directively controlled automatic switches forestablishing a connection between a calling and a called automatictelephone line over said trunk line` and means automatically operativewhen a manual telephone line is extended to said trunk line forextending said connection to said operators position.

12. In a telephone system, manual and automatic telephone lines, a lineswitch associated with each telephone line, a trunk line, an operatorsposition, automatic switches, means for directively controlling certainof said automatic switches from a calling one of said automatictelephone lines to establish a connection with a called one of saidtelephone lines over said trunk line, means operative over one of lsaidmanual telephone lines for seizing said trunk line, and means operativeas a result of such seizure for extending said connection to saidoperators position.

13. In a telephone system, manual and automatic telephone lines, a lineswitch associated with each telephone line, a trunk line, an operatorsposition, automatic switches, means for directively controlling certainof said automatic switches from a calling one of said automatictelephone`lines to establish a connection with a called one of saidtelephone lines over said trunk line, means operative over one of saidmanual telephone lines for seizing said trunk line, and means operativeas a result of such seizure for extending said connection to saidoperators position, and means for operating certain of said automaticswitches from an automatic telephone line to extend a connection to saidoperators position.

14. In a telephone system, manual and automatic telephone lines, a lineswitch associated with each telephone line, a trunk line, an operatorsposition, automatic switches, means for directively controlling certainof said automatic switches from a calling one of said automatictelephone lines to establish a connection with a called one ofsaidtelephone lines over said trunk line, means operative over one ofsaid manual telephone lines for seizing said trunk line, means operativeas a result of such seizure for extending said connection to saidoperators position, and means for operating certain of said automaticswitches from an automatic telephone line to extend a connection to saidoperators position over said trunk line.

15. In a telephone system, a rst and a second exchange trunk lineextending between said exchanges, telephone lines at each exchange,automatic switches in each exchange, means for establishing a connectionbetween the telephone line in one exchange by certain of said automaticswitches in each exchange over said trunk line, an operators position atthe second exchange, and means including said automatic switches and oneof said trunk lines for extending a telephone line at the first exchangeto said operators position.

16. In a telephone system, a trunk line terminating in a selector, saidswitch having ten levels of bank contacts and a normal level of bankcontacts, means for directively operating said switch over said trunkline to select any one of said ten levels, and means automaticallyoperative over said trunk line to initiate the rotation o! said switchon its normal level.

17. In a telephone system, a rst exchange and a second exchange,telephone lines in each exchange, trunk lines connecting said exchanges,automatic switches in each exchange, a plurality of operators positionsat said second exchange, means including certain of said automaticswitches at each exchange and one of said trunk lines for establishing aconnection between a telephone line in each exchange, and means forestablishing a connection from a calling line in the iirst exchange toone operators position over certain of said trunk lines and to anotheroperators position over certain other of said trunk lines.

18. In a telephone system, a iirst and second exchange, trunk linesconnecting said exchanges, telephone lines in each exchange, automaticswitches in each exchange, means including certain of said automaticswitches in each exchange and any one of said trunk lines forestablishing connections between the lines in the ilrst exchange andsecond exchange, a plurality of operators positions, means forassociating each operators position with a group of said trunk lines,and means operative from a calling line in the rst exchange to establisha connection with any one of said operators positions solely over one ofthe associated trunk lines.

19. In an automatic telephone system, a main exchange and a subexchange, telephone lines in said sub exchange, rst selectors in saidmain exchange, trunk lines connecting said sub and main exchanges, meanscontrolled over one oi.' said trunk lines from a telephone line in thesub exchange for directively controlling one of said ilrst selectors, asecond main exchange, and means controlled from said second mainexchange over one of said trunk lines for initiating the automaticoperation of one of said first selectors.

20. In a telephone system, manual and automatic lines, a trunk lineterminating in an automatic switch, an operators position, directivelycontrolled automatic switches for establishing a connection between acalling and called automatic telephone line over Asaid trunk lineincluding said automatic switch and means operative when a manualtelephone line is extended to said trunk line for automaticallyoperating said switch to extend the connection to said operatorsposition.

21. In a telephone system, an automatic switch, a plurality of groups oftrunk lines accessible to said switch, another group of trunk linesacces-v sible to said switch means for directively controlling saidswitch to select any group of said trunk lines of said plurality andmeans for initiating the automatic operation of said switch to select atrunk line in said other group.

22. In a telephone system, a first exchange, an intermediate exchange, athird exchange, a selector in the iirst exchange, trunk lines leadingfrom a level of said selector to the third exchange, a trunk line at theend of said level leading to the intermediate exchange, selector andconnector switches in the third exchange, means responsive to theoperation of the iirst said selector for seizing an idle trunk in saidlevel leading directly to the third exchange to extend the calling lineto a selector in said third exchange, means for operating the connectorand selector in the third ei'. 1nge to extend the calling line to acalled line in the third exchange, means whereby ii all *he trunks insaid level are busy the iirst said selector will select a trunk at theend of said level leading to the intermediate exchange, a selectorswitch at the end of said trunk in the intermediate exchangeautomatically operated responsive to seizure of the trunk to extend thetrunk to a said selector in the third exchange, and means whereby saidselector and the connecto-r in the third exchange may be operated toextend the calling line in the iirst exchange to a called line in thethird exchange.

23. In a telephone system, a first exchange, an intermediate exchange, athird exchange, a selector in the first exchange, trunks from a singlelevel of said selector leading directly to the intermediate and thirdexchanges respectively, selector and ,onnector switches in thethirdexchange, and means whereby if all of the trunks leading directlyto the third exchange are busy the call will be extended over' a saidtrunk to the intermediate exchange and automatically to a selector inthe third exchange, whereby a call from a calling line in the rstexchange may be extended to a called line in the third exchange bydirect or indirect trunking responsive to the same number of digits sentfrom the calling line.

24. In a telephone system, a iirst exchange, an intermediate exchange, athird exchange, a selector in the rst exchange, trunks from a singlelevel of said selector leading directly to the intermediate and thirdexchanges respectively, selector and connector switches in the thirdexchange, and means whereby if all of the trunks leading directly to thethird exchange are busy the call will be extended over a said trunk tothe intermediate exchange and automatically to a selector in the thirdexchange, whereby a call from.

a calling line in the first exchange may be extended to a called line inthe third exchange by direct or indirect trunking responsive to the samenumber of digits sent from the calling line, said indirect trunkingconnection having more switches than the direct trunking connection butincluding an automatically operated switch to extend the connection fromthe first exchange over a 'said trunk through the intermediate exchangeto the third exchange.

25. In a telephone system, a trunk line extending from the rst exchangeto the second exchange, a lrepeater associated with said trunk line inthe first exchange, a selector switch associated with said trunk line insaid second exchange, said trunk line having a plurality of branches atthe first exchange, means operative over said trunk line when seizedover one of said branches for bridging the trunk branch conductors fordirectively controlling said selector, and means operative as a resultof seizing said trunk line over another of said branches for groundingone of the trunk branch conductors for automatically operating saidselector.

26. In a telephone system, a trunk line extending from the firstexchange to the second exchange, a repeater associated with said trunkline in the iirst exchange, a selector switch associated with said trunkline in said second exchange, said trunk line having a plurality ofbranches at the first exchange, means operative over said trunk linewhen seized over one of said branches for bridging the trunk branchconductors for directively controlling said selector, and meansoperative as a result of seizing said trunk line over another of saidbranches for grounding one of the trunk branch conductors forautomatically operating said selector, one of the two latter said meansincluding bridging the trunk conductors of one branch and the othermeans including the grounding of one `of the trunk conductors of theother branch.

27. In a telephone system, a trunk line extending from a iirst exchangeto a second exchange, a selector switch terminating said trunk line insaid second exchange, two branches for said trunk line at the rstexchange, selector switches for connecting with said branches, means lorbridging the branch conductors oi one branch when selected by a selectorfor causing the selector in the distant exchange to operate as adirective selector switch, and means for grounding one of the conductorsof the other branch when selected by a selector switch to cause theselector in the second switch to automatically operate as a rotaryswitch over a normal level thereof.

MILTON S. FRIENDLY, CENTRAL REPUBLIC BANK AND 'I'RUST COMPANY,Coezecutors of the Estate of Herbert M.

Friendly, Deceased, GREENBAUM,

By CHARLES J.

- Assistant Trust Oicer.

